The invention is based on a fuel injection pump as defined hereinafter. In a known fuel injection pump of this kind, the control of the pressure acting upon the movable wall in the manner of a restoring force is effected with the aid of both a pressure limiting valve and an electromagnetically actuated switching valve. The electromagnetically actuated switching valve is controlled by a control unit, in accordance with a plurality of operating parameters, such that it is closed during cold starting and during the warmup phase. As a result, the pressure in the control pressure chamber is capable of rising very rapidly immediately after fuel injection pump operation begins. The discharge opening is closed by the movable wall at this time, and the pressure on the pressure side of the pressure control valve or in the work chamber of the injection adjusting device very quickly assumes high values in terms of a shift of the instant of injection toward "early". The pressure being established on the pressure side of the fuel feed pump or in the work chamber of the injection adjusting device is limited by the instant of opening of the pressure limiting valve, so that beyond a predetermined fuel injection pump rpm the pressure in the work chamber is not increased further. With an embodiment of this kind, the warmup behavior per se of the internal combustion engine is improved; however, shifting the instant of injection forward is often insufficient to generate smooth engine operation immediately after starting. Especially in the cold state, because of increased friction, engine power losses are so great that at a given injection quantity the idling rpm would decrease considerably. Various proposals have accordingly been made for increasing either the fuel injection quantity, or the idling rpm, during the warmup phase by suitable means.
From German Offenlegungsschrift No. 28 44 910, it is known to increase both the instant of injection and the idling rpm simultaneously by means of a thermostatically actuated mechanical device. In this apparatus, by means of a thermostatic element via a suitable coupling linkage, a mechanical member determining the instant of injection is adjusted, and simultaneously the idling stop, which determines power, on the adjusting member of the fuel injection pump is varied. This adjusting lever is connected to an adjusting member for the biasing the main governor spring, which acts upon a governor lever which on the one hand is acted upon by an rpm-dependent force and on the other hand actuates a quantity adjusting device of the fuel injection pump. This apparatus has the disadvantage that the injection onset adjustment takes place mechanically, and the setting is fixed at a predetermined adjustment angle. Complicated mechanical provisions must also be made in order to effect this adjustment. An engagement opening must be provided in the pump housing, which interrupts the guidance of the cam element or roller ring element effecting the drive of the pump piston of the engine, and this is expensive. Furthermore, the roller ring segment or cam ring element requires a recess for the mechanical adjusting element to engage. Not only does this occasion additional engineering and manufacturing expense, but it generally results in reducing the mechanical strength of the parts and causes an impairment in the bearings of these parts.